Production of carbon black from coal

ABSTRACT

A method and apparatus for producing carbon black by pyrolytic decomposition of coal with hot combustion gases. In a cylindrically shaped vertical reactor coal is tangentially introduced, thus establishing a helically flowing mass of pulverized coal. This mass is contacted with hot combustion gases. Fine ashes are withdrawn from the upper portion of the reactor at the periphery and coarse ashes are withdrawn from the lower portion of the reactor from the periphery. Carbon black-containing gases are withdrawn from the area of the vertical axis of the reactor overhead.

This application is a continuation-in-part of my copending applicationSer. No. 393,492, filed Aug. 31, 1973, now abandoned.

This invention pertains to the production of carbon black from coal. Inone of its more specific aspects, this invention pertains to a methodand apparatus for the production of carbon black from coal, the carbonblack containing minimal quantities of ash.

The production of carbon black from coal is well known from such priorart as that disclosed in U.S. Pat. No. 3,424,556, the disclosure ofwhich is incorporated herein by reference, the operating conditions oftemperature and pressure of that method being employable in the methodof the present invention. Using pulverized coal as a feed to a carbonblack reactor becomes increasingly attractive as liquid hydrocarbonfeedstock prices increase.

The formation of carbon black from coal involves an initialdecomposition of the coal to tar, ash, and gaseous hydrocarbons. The tarhydrocarbons are subsequently dehydrogenated and the carbon aggregatedto form carbon black. In contrast, in the production of carbon blackfrom a liquid hydrocarbon, because the hydrocarbon need not be convertedfirst to tar, the use of coal requires a longer residence time.Relatedly, the residence time of the product black in the reactor mustbe prolonged to enable separation of the ash from the carbon black.

The method and apparatus of this invention are particularly suited forthese purposes. In accordance with this invention a helically flowingmass of pulverized coal is established in a cylindrical reactor, thispulverized coal is contacted with hot combustion gases, and the carbonblack-containing smoke is withdrawn overhead along the vertical axis ofthe reactor. Because of the centrifugal forces established within thechamber, only minimal quantities of ash will move into the centralvortex area of the chamber and so only minimal quantities of ash will bemixed with the carbon black and removed upwardly from the chamber. Aprolonged residence time of the coal particles is achieved inasmuch asonly a limited quantity of ash will be removed from a reactor throughupper and lower ash removal ports.

In accordance with this invention there is thus provided a method forproducing carbon black from coal comprising introducing pulverized coalsuspended in a suspending stream of oxidant gas tangentially through theperiphery of a vertically positioned reactor to establish the coal as ahelically flowing mass proximate the wall of the reactor, introducinghot combustion gases formed by the combustion of fuel gas and an oxidantgas, as well as primary oxidant gas upwardly into the reactor toward thelocus of introduction of the coal, forming a mixture comprising the coaland the hot combustion gases, reacting the mixture to produce carbonblack and ash from the coal, passing the carbon black inwardly towardthe vertical axis of the reactor, introducing secondary oxidant gasupwardly along the vertical axis of the reactor into contact with thecarbon black to increase the photelometer of the carbon black,withdrawing a first stream comprising ash formed in the reacting steptangentially through the periphery of the reactor proximate to the upperterminus of the reactor, withdrawing a second stream comprising ashformed in the reacting step tangentially through the periphery of thereactor proximate the lower terminus of the reactor and withdrawingcarbon black overhead from the reactor along the vertical axis of thereactor.

In accordance with one presently preferred embodiment of this invention,fuel gas is introduced into the reactor through a separate inlet closeto the inlet of the coal. This separate inlet can be located as a nozzleinside of the entry port of the coal. This additional fuel gas isignited and combusted in the reactor and serves to preheat the coal.

The present invention can be carried out employing any kind ofpulverized coal. Presently preferred are coals selected from the groupconsisting of anthracites, semianthracites, bituminous andsemibituminous coals, and mixtures thereof. The coal is preferablycomminuted to at least 200 to 400 mesh (US. sieve) although particlessmaller than 400 mesh can be employed. The coal preferably has amoisture content of less than 3 weight percent of water and a maximumash content of less than about 15 weight percent. In the presentlypreferred embodiment the coal will have been ground and/or charred to astate in which it will almost begin to agglomerate.

Throughout this specification the term "oxidant gas" is to be understoodto be a gas selected from the group consisting of air, oxygen-enrichedair and oxygen.

"Hot combustion gases" in this specification means the combustionproduct of a gaseous fuel, e.g., natural gas, and an oxidant gas. Inevery instance where hot combustion gases are introduced into thereactor it is to be understood that essentially two differentpossibilities are encompassed. First, the hot combustion gases can beproduced outside of the reactor and can then be introduced into thereactor. Second, the gaseous fuel and the oxidant gas can be separatelyintroduced into the reactor and combusted in the reactor. The secondpossibility is generally preferred since hot combustion gases do nothave to be passed through conduits.

The quantity of gaseous fuel introduced as hot combustion gases into thereactor is sufficient to supply from about 3300 to about 4600 BTU perpound of coal introduced. From this value the quantity of gaseous fuelto be introduced can readily be determined from the number of BTU's perstandard cubic foot of the gaseous fuel and the number of pounds of coalused.

The pulverized coal in the carrier oxidant gas is tangentiallyintroduced into the reactor. The axial location of the tangentialintroduction port for the coal through the circumferential periphery ofthe reactor is proximate the midpoint of the vertical axis of thechamber. The coal is introduced through at least one pair of conduitsopening tangentially into the reactor in order to establish the mass ofhelically flowing pulverized coal.

Both the hot combustion gases and the primary oxidant gas are introducedinto the reactor through its periphery and in axially upward directionfrom orifices located below the locus of introduction of the coal. Thesegases are moved upwardly so as to maintain the coal and ash as floatingparticles within the reaction zone and to prolong the residence time ofthe carbon in the reactor.

The primary air can be introduced through separate inlets. It is,however, within the scope of this invention to introduce the hotcombustion gases into the reactor together with the primary air. In thelatter case oxygen-rich hot combustion gases are introduced into thereactor which means that more oxidant is introduced than necessary for astoichiometric combustion of the gaseous fuel. The surplus of remaininggaseous oxidant then constitutes the primary gaseous oxidant.

The total quantity of gaseous oxidant to gaseous fuel is above the rangestoichiometrically necessary. In the case of the use of natural gas asthe gaseous fuel and air as the oxidant gas, this ratio will be in therange of about 13:1 to about 19:1 SCF of air per SCF of natural gas. Thetotal quantity of oxidant gas encompasses both the primary oxidant gasand the oxidant gas which is used as the reactant to produce the hotcombustion gases.

The discharge rate of the primary oxidant and the hot combustion gasesin the reactor is within the range of about 10 to about 20 ft./sec. soas to have a velocity of these gases within the range of about 3 toabout 7 ft./sec. at a distance of about 1 ft. from the nozzles throughwhich the gases are introduced into the reactor. Preferably the gaseousoxidant is introduced upwardly into the reactor in the absence ofsimultaneous introduction therewith of any fuel. Thus the combustion ofthe fuel occurs in the reactor. In either instance the gaseous oxidantwill be introduced at a rate to produce a zone between the carbon blackwithdrawal outlet and the inner wall of the reactor in which thehelically flowing gases are at a velocity within the range of about 40to about 100 ft./sec.

The secondary oxidant gas introduced upwardly along the vertical axis ofthe reactor will be introduced in a quantity sufficient to adjust thephotelometer of the carbon black to the desired value. Preferably thesecondary gaseous oxidant will be introduced in an amount within therange of about 4 to about 16 SCF per pound of coal. More importantly,however, the secondary gaseous oxidant will be introduced along thevertical axis of the reactor in a plurality of jet streams. Thedischarge velocity of these jet streams is within the range of about 20to about 80 ft./sec. As this secondary gaseous oxidant moves upwardlyalong the vertical axis of the reactor, during which time the carbonblack moves inwardly toward it, the velocity of the secondary gaseousoxidant column will be within the range of about 8 to about 30 ft./sec.at a distance of about 2 feet from the locus of discharge of these jets.

The carbon black reactor is adapted with at least two pairs of ashremoval ports. One pair of ports proximate the wall closing the upperend of the chamber opens tangentially from the chamber through itscircumferential periphery and is used to remove the fine ash. At leastone second pair of ports is positioned proximate the wall closing thelower end of the chamber, the ports opening tangentially from thechamber through its circumferential periphery and being used to removethe coarse ash.

The coal flowing in a helically moving layer from the ports ofintroduction is contacted with the hot combustion gases which areintroduced radially through the periphery of the reactor and upwardlytoward the locus of introduction of the coal. The coal is contacted withthe hot combustion gases to produce carbon black and ash. The carbonblack passes inwardly from the helically flowing mass into the core areaof the reactor. The carbon black-containing gas is then withdrawn fromthe reactor through an exit conduit opening from the reactor along thevertical axis thereof in upward direction. The carbon black-containinggas thus is removed overhead from the reactor.

The method and apparatus of this invention will be further understood byreferring to the attached drawing illustrating a preferred embodiment ofthe invention.

FIG. 1 is a view in elevation of the reactor and

FIG. 2 is a plan view of the reactor through section 2--2 of FIG. 1.

Referring now to the drawings there is shown the reactor which will becomprised of a preferably circular chamber 10 having a diameter Dv and aheight Hv.

The chamber will be adapted with at least one of coal-introductory ports17 and 18 which will open tangentially into the chamber at a locuslocated a distance above the entrance 21 into carbon black smoke outletconduit 15. Carbon black smoke outlet conduit 15 will have a diameter Dcand its entrance 21 will be located a distance Lc vertically downwardlyfrom at least one of fine ash exit ports 11 and 12. These ports willopen tangentially from the chamber through its outer periphery at adistance b above the tangential-opening coal introductory ports 17 and18. Ports 17 and 18 will open into the vessel to discharge coal in afirst, for example, counterclockwise direction as viewed in FIG. 2; atleast one of ports 11 and 12, also, will open from the vessel proximatethe upper wall to discharge fine ash from the vessel in the first, orcounterclockwise, direction as viewed in FIG. 2.

Opening into the chamber at a distance c below entrance 21 of conduit 15will be at least one conduit 16 through which oxidant gas, namely air,oxygen, or oxygen-enriched air, is introduced. Gaseous fuel ispreferably introduced through separate conduits. As indicated earlier,however, it is also possible to introduce the hot combustion gasesthrough conduits 16. These conduits discharge upwardly into the chamberat a plurality of loci as shown in FIG. 2 and will discharge, preferablyno farther from the wall of the chamber than is a vertical center line25 through, and common to, conduit ports 11 and 17 and through, andcommon to ports 12 and 18.

Conduits 13 and/or 14 are at least one coarse ash exit port openingtangentially from the chamber through its circumferential periphery inthat direction in which fine ash exit ports 11 and 12 exit from thechamber at a locus just above the lower closing wall of the chamber.

Opening into the chamber through its lower wall is at least onesecondary air inlet port 19. Preferably a plurality of such ports willopen upwardly into the chamber in any suitable number, preferably fouror more, on a common circle 20 which will be positioned as definedhereinafter relative to the diameter of carbon black outlet conduit 15.

As stated previously, only a limited quantity of ash will be removedfrom the chamber through the ash removal ports in order to control theresidence time of the reactants within the reaction chamber. A residencetime of up to two seconds will be required and this residence time iscontrolled by butterfly, or choke, valves 30 and 31 positioned in theash removal conduits opening from the vessel. Relatedly, since largequantities of coal fines or ash are undesired in the carbon blackproduct, the product is monitored to facilitate adjustment of the valvesin the ash outlet lines. The valves in the ash outlet lines 11 and 12can be positioned as shown by valves 30 and 31 of FIG. 2, thecorresponding valves in conduits 13 and 14 not being shown but beingsimilarly designed and positioned.

While variations from the dimensions and ranges set forth herein arefeasible, the following ranges will serve to facilitate the design ofreactors within the ranges given.

Chamber 10 will have a diameter of from about 3 to about 7 feet and aheight of from about 10 to about 30 feet.

Coal introductory ports 17 and 18 will be from about 6 to about 15inches in diameter and will be positioned from about 2 to about 6 feetabove entrance 21 into conduit 15.

Conduit 15, the carbon black outlet conduit, will have a diameter offrom 1 to about 2 feet and will extend downward from wall 32 closing theupper end of the chamber by a distance within the range of from 5 to 14feet.

Conduits 11 and 12 which will serve as fine ash exit ports will vary innumber from about 2 to about 8 and will have diameters of from 1 to 4inches and be positioned, centerline to centerline, a distance of fromabout 3 to about 8 feet above ports 17 and 18.

Conduits 13 and 14 which will serve as coarse ash exit ports will varyin number from about 2 to about 8 and will be positioned with theirdownstream wall coincident with the lower wall 33 of the chamber andwill have a diameter of from 2 to about 6 inches.

Conduits 16 which serve as primary air and fuel entry ports can varyfrom about 4 to about 16 in number and will be positioned to dischargeupwardly from a locus positioned from about 3 to about 9 feet belowentrance 21 of conduit 15.

Conduits 19, which serve as secondary air inlets, can vary from about 4to about 16 in number and will be positioned a distance of from about1/4 foot inside the projected circumference of conduit 15 to about 1/3foot outside the projected circumference of conduit 15.

While, in the previous discussion, air and fuel are considered as beingintroduced into the reactor, it is to be understood that they can beintroduced in the form of hot combustion gases formed by the oxidationof the fuel with the air, or other gaseous oxidant.

In a preferred embodiment of this chamber, which will be operable underthe conditions defined below, the chamber will have a diameter of 4.5feet and a height of 16 feet. carbon black will be removed through one1-1/4 foot diameter conduit extending downwardly into the chamber adistance of about 8 feet.

Pulverized coal and air will be introduced through two 10 inch diameterconduits positioned 3 feet above the entrance into the carbon blackoutlet conduit. Fuel will be introduced through a separate conduitinside of said 10 inch diameter conduit.

Two fine ash exit ports will be provided, these being 1-1/2 inches indiameter and being located a distance of about 8 feet above the entranceinto the carbon black outlet conduit.

Two coarse ash exit ports will be provided, these being 3 inches indiameter and being located with their upstream walls coincident with thelower wall of the chamber.

Eight primary air and fuel entry ports of 2 inches diameter will beprovided, these being equally spaced around the chamber and dischargingon a locus about 5 feet below the entrance into the carbon black outletconduit.

Eight secondary air inlet ports will be provided, these being equallyspaced around the chamber on the circle having the circumference ofconduit 15, the circle coinciding with the projection of conduit 15.These secondary air inlet ports will have a diameter of 1 inch, and willbe positioned to discharge at about floor level.

Employing the reactor described in the preferred embodiment, under thepreceding conditions, feeding semibituminous coal continuously into thechamber, calculated operating and production conditions will be asfollows:

    Coal Charged                                                                  Pounds per hour           1600                                                Mesh                      200-400                                             Residence time, sec.      11/4                                                Air and Fuel                                                                  With Coal Through Ports 17 and 18                                             Air, SCFH                 75,000                                              Fuel, (Natural Gas) SCFH (through                                              a separate pipe)         4,400                                               Via Conduits 16, as Hot Combustion Gases                                      Air, SCFH (primary air and air                                                 necessary to combust the fuel)                                                                         25,000                                              Fuel, (Natural Gas) SCFH (through                                              a separate pipe)         1,660                                               Air Via Conduits 19                                                            Air, SCFH (secondary)    8,000                                               Production                                                                    Fine Ash, Lbs./Hr.        50                                                  Gases with Fine Ash, SCFH 1,000                                               Coarse Ash, Lbs./Hr.      180                                                 Gases with Coarse Ash, SCFH                                                                             4,000                                               Operating Conditions                                                          Temperature, °F    2300-2700                                           Pressure, psia            19                                                  Smoke                                                                         Gases, SCFH               120,000                                             Carbon Black, Lbs./Hr.    620                                                 Carbon Black Properties (Estimated)                                           Nitrogen Surface Area, m.sup.2 /gm.                                                                     80                                                  Dibutylphthalate No., DBP, cc/100 g.                                                                    105                                                 Photelometer              90                                              

The reactor will be operated by introducing hot combustion gases into asuitably insulated reactor. The insulating material preferably issilmanite. When the reactor temperature reaches about 2700° F thepulverized coal is introduced in an air stream and the introduction ofsecondary air will be made simultaneously. The valves in the ash outletconduits will be regulated to provide a maximum residence time. Thequantity of pulverized coal introduced will then be increased until thecarbon black contains a maximum-allowable quantity of ash, the quantityof secondary air, which can be preheated as can any of the other of thereactants, being increased until the carbon black has the desiredphotelometer. The carbon black, in the form of smoke, can be quenchedand recovered from the smoke in the conventional manner.

Reasonable variations and modifications, which will be apparent to thoseskilled in the art, can be made in this invention without departing fromthe spirit and scope thereof.

I claim:
 1. A method of producing carbon black from coal comprisinga.introducing pulverized coal suspended in a suspending stream of oxidantgas tangentially through the periphery of a vertically positionedreactor to establish said coal as a helically flowing mass proximate thewall of said reactor; b. introducingaa. hot combustion gases formed bythe combustion of fuel gas and an oxidant gas; as well as bb. primaryoxidant gas upwardly into said reactor toward the locus of introductionof said coal; c. forming a mixture comprising said coal and said hotcombustion gases; d. reacting said mixture to produce carbon black andash from said coal; e. passing said carbon black inwardly toward thevertical axis of the reactor; f. introducing secondary oxidant gasupwardly along the vertical axis of said reactor into contact with saidcarbon black to increase the photelometer of said carbon black; g.withdrawing a first stream comprising ash formed in step (d)tangentially through the periphery of said reactor proximate to theupper terminus of said reactor; h. withdrawing a second streamcomprising ash formed in step (d) tangentially through the periphery ofsaid reactor proximate the lower terminus of said reactor; i.withdrawing carbon black overhead from said reactor along the verticalaxis of said reactor.
 2. The method of claim 1 in which said oxidant gasis air and the ratio of air introduced in step (b), consisting ofoxidant air and primary air, to fuel introduced in step (b) is in therange of 13 SCF air per SCF of fuel to 19 SCF air per SCF of fuel andsaid fuel is introduced in such a quantity to supply about 3300 to about4600 BTU per pound of said coal introduced.
 3. The method of claim 1 inwhich said secondary oxidant is air which is introduced in a quantity ofabout 4 to about 16 SCF per pound of coal introduced into the reactor.4. A method in accordance with claim 2 wherein said primary air isintroduced into said reactor at a velocity within the range of about 10to about 20 ft./sec.
 5. A method in accordance with claim 3 wherein saidsecondary oxidant is introduced in a plurality of streams at a velocitywithin the range of about 20 to about 80 ft./sec.